Use of carbonyl nickel in nickel-chromium-tungsten alloys



A. T. CAPE March 2, 1965 2 Sheets-Sheet 1 Filed Aug. 2'7, 1963 INVENTOR.

March 2, 1965 A. T. CAPE 3, 7 ,739

USE OF CARBONYL NICKEL IN NICKELCHROMIUM-TUNGSTEN ALLOYS Filed Aug. 2'7. 1963 2 Sheets-Sheet 2 IN VEN TOR. Aer/7w TCfl f United States Patent Arthur T. Cape, Monterey, Calitl, 'assignor, by mesne assignments, to Coast Metals, Inc, Little Ferry, Ni, a corporation of Delaware Filed Aug. 27,1963, Ser. No. 304,856 3 Claims. ((31. 75-434) This invention relates generally to the use of carbonyl nickel in nickel-chromium-tungsten alloys, but has reference more particularly to the use of such nickel in alloys of the type described in my US. Patent No. 2,481,976.

In the aforesaid US. patent, there is described an alloy which is stated to resist corrosive action of lead oxide at high temperatures, this alloy containing from about 35 to about 75% nickel, from about 25 to about 40% chromium, from about 4 to about 9% tungsten, cobalt in amounts up to about 12%, and from about 1 to about 3.5% carbon, the balance of the alloy being iron, but the iron being not in excess of and the nickel being always in excess of the chromium.

It has been discovered, however, that the alloy is not entirely resistant to the corrosive action of lead oxide. In seeking an explanation for this, it was found that although the matrix of the alloy resists such corrosive action, the carbides in the alloy, which are readily attacked by lead oxide, are of such form and are so close to each other, that the attack by lead oxide is virtually continuous from one carbide to the other, causing a virtual breakdown of the alloy, as the result of the attack.

I have discovered that if carbonyl nickel, that is, nickel produced by the Mond process, is used in producing the alloy of Patent No. 2,481,976, in an amount sufficient to provide from to 100% of the total nickel content of the alloy, that this causes the carbides to become so dispersed or separated from each other that when the alloys are attacked by lead oxide at high temperatures, the attack is confined to the carbides and is resisted by the relatively large intervening areas of matrix, thereby preserving the alloy against continuous attack, with the result that the alloy has a considerably longer life than does the same alloy, in which all of the nickel is in the form of electrolytic nickel. In general, I prefer that about 25% of the total nickel content of the alloy be in the form of carbonyl nickel.

The use of carbonyl nickel, in the proportions stated, as a part of the nickel constituent of the alloy, may thus be extended to alloys of the following compositions:

Ran e. Preferred Preferred percent Range, Alloy.

percent percent Nickel 35 75 Balance 62. 2 Chromium 2540 25-30 25. 6 Tungsten 4-10 7-9 8. 6 Cobalt .1 to 6 .1-1. 0 .1 Carbon 1 to 3.51 1.52.75 1. 9 Silicon l. 50 max. 1 50 max. 6 Managan l. 00 max. 1. 00 max .5 ron 10 max. 3 00 max .5

ice

FIG. 2 shows the microstructure, at the same magnification, of an alloy of identical composition, as in FIG. 1, but in which all of the nickel was supplied in the form of carbonyl nickel.

FIG. 3 shows the microstructure, at a magnification of 250x, of an alloy consisting of 58.3% nickel, 25.6% chromium, 8.6% tungsten, 4% cobalt, 1.9% carbon, .6% silicon, .5% manganese, and .5 iron, and in which all of the nickel was supplied as electrolytic nickel.

FIG. 4 shows the microstructure, at the same magnification, and of an alloy of identical composition as in FIG. 3, but in which 25% of the nickel was supplied in the form of carbonyl nickel.

FIG. 5 shows the microstructure, at the same magnification, and of an alloy of identical composition as in FIG. 3, but in which 50% of the nickel was supplied in the form of carbonyl nickel.

FIG. 6 shows the Inicrostructure, at the same magnification, and of an alloy of identical composition as in FIG. 3, but in which of the nickel was supplied in the form of carbonyl nickel, and

. FIG. 7 shows the microstructure, at the same magnification, and of an alloy of identical composition as in FIG. 3, but in which all of the nickel was supplied in the form of carbonyl nickel.

FIG. 1 shows that the carbides, which are the white areas, in dendritic form, are relatively close to each other, and in some areas actually connected with each other, thus leaving relatively small areas of matrix therebetween, with the result, that when the carbides, which are readily attacked by lead oxide at high temperatures, are attacked, the attack is virtually continuous from one carbide to another, causing a virtual breakdown in the alloy, as the result of the attack.

FIG. 2 shows that the carbides, which are the large white areas of elongated or acicular form, are dispersed or separated from each other by relatively large areas of matrix, so that when the carbides are attacked by lead oxide at high temperatures, the attack is confined to the carbides, and resisted by the relatively large intervening areas of matrix, thereby preserving the alloy against continuous attack, with the result that the alloy, as a whole, has a considerably longer life than does the alloy of FIG. 1.

FIG. 3 shows that the carbides, which are the light areas, of elongated or acicular form, are virtually contiguous with each other, with the result that when the carbides are attacked, the attack progresses rapidly throughout the entire structure, causing a virtual breakdown or destruction of the part, which may be a valve.

FIG. 4 shows that the carbides, which are the white areas, are elongated but not in closely spaced relation with each other. Although the carbides are not essentially of euhedral form, they are nevertheless so dispersed or separated from each other that when the carbides are attacked by lead oxide at high temperatures, the attack is confined to the carbides, and resisted by the relatively large intervening areas of matrix, thereby preserving the alloy against continuous attack, with the result that the alloy, as a whole, has a considerably longer life than does the alloy of FIG. 3.

FIG. 5 shows that the carbides, which are the White grains or areas, in addition to being separated from each other, in a desired manner, are also of euhedral form. This alloy, as does the alloy of FIG. 4, has a considerably longer lite, under attack of lead oxide at high temperatures, than does the alloy of FIG. 3.

FIG. 6 shows that the carbides, which are the large white grains, are well separated from each other, and are also of euhedral form. This alloy, as compared with that of FIG. 3, also has a long life under attack of lead oxide at high temperatures.

3 FIG. 7 shows a structure similar to that of FIG. 4, but containing more carbides of euhedral form. This alloy, as compared with that of FIG. 3, also has a long life under attack of lead oxide at high temperatures.

Although it is preferred that the alloy contain less than 1% cobalt, it is difiicult, as a practical matter, to prepare or make the alloy with so low a cobalt content. On the other hand, it has been found that without some cobalt in the alloy, there is a tendency for the molten material to contain gas, resulting in defective castings and weld deposits which are not free from porosity. It has been found that additions of cobalt, in amounts of not" more than 6%, do ameliorate these conditions. 1 H 1 a The eifect of the use of carbonyl nickel, in prolonging the life of the aforesaid alloys, becomes significant when 15% of the nickel content of the alloy is supplied in the form of carbonyl nickel, and reaches an optimum when 25% of the nickel content of the alloy is supplied in the form of carbonyl nickel. Beyond this point, that is to say, when more than 25% of the nickel content, and

up to 100% of the nickel content, is-supplied in the form of carbonyl nickel, the life of the alloy under lead oxide attack at high temperatures is not increased appreciably over the life of the same alloy in which 25 of the nickel is in the form of cabonyl nickel. However, in view of the somewhat greater cost of carbonyl nickel than electrolytic nickel, it is not advisable, for reasons of econom to use carbonyl nickel in an amount greater than about 50% of the nickel contentof the alloy.

It will be understood that slight changes may be made in the alloys, without department from the spirit of the invention or the scope of the appended claims. The expression, the balance of thealloy being substantially all iron, as used in the claims, is intended to permit the inclusion, in the alloy, of small or residual amounts of silicon, in amounts up to a maximum of about 1.5%, and manganese, in amounts'up toa maximum of about 1.0%.

This is a continuation-in-part of my copending application, Serial No. 62,330, filed October 13, 1960, now abandoned.

' Having thus described my invention, I claim:

1. An alloy consisting of from about 35% toabout 75% nickel, about 25% to about 40% chromium, about 4% to about 10% tungsten, about 0.1% to about 6% cobalt, about 1% to about 3.5% carbon, and the balance substantially all iron, the iron content not to exceed 10%, from about 15% to about 100% of the nickel constituent of the alloy being provided as carbonyl nickel when said alloy is produced, said alloy being characterized in that the carbides existing therein are dispersed in a metal matrix whereby when said alloy is exposed to attack by lead oxide at high temperatures, the alloy resists such attack and has a considerably longer life than does the same alloy in which more than about 85% of the nickel is provided in the form of electrolytic nickel and in which the carbides are not dispersed to the same extent.

2. An alloy consisting of from about 25% to about 30% chromium, from about 7% to about 9% tungsten, from about 0.1% to about 1% cobalt, from about 1.5% to about 2.75 carbon, silicon up to a maximum of about 1.50%, manganese up to a maximum of about 1.44%, iron up to a maximum of about 3.00%, and the balance of the alloy being substantially all nickel, the nickel content not to exceed of which from about 15% to about 100% is provided as carbonyl nickel when said alloy is produced, said alloy being characteriz'ed in that the carbides existing therein are dispersed in a metal matrix whereby when said alloy is exposed to attack by lead oxide at high temperatures, the alloy resists such attack and has a considerably longer life than does the same alloy in which more than about of the nickel is provided in the form of electrolytic nickel and in which the carbides are not dispersed to the same extent.

3. The method of making alloys consisting of from about 35% to about 75% nickel, about 25% to about 40% chromium, about 4% to about 10% tungsten, about 0.1% to about 6% cobalt, about 1% to about 3.5% carbon, and the balance substantially all iron, the iron content not to exceed 10%, which consists in introducing from about 15% to about of the nickel constituent of said alloy in the form of'carbonyl nickel.

References Cited in the file of this patent UNITED STATES PATENTS 2,396,552 Cape Mar. 12, 1946 2,458,502 Cape Jan. 11, 1949 2,481,976 Cape Sept. 13, 1949 2,826,494 Drummond Mar. 11, 1958 OTHER REFERENCES Bray: Non Ferrous Production Metallurgy, 2nd edition, 1947, paragraphs 505507 and 516. 

1. AN ALLOY CONSISTING OF FROM ABOUT 35% TO ABOUT 75% NICKEL, ABOUT 25% TO ABOUT 40% CHROMIUM, ABOUT 4% TO ABOUT 10% TUNGSTEN, ABOUT 0.1% TO ABOUT 6% COBALT, ABOUT 1% TO ABOUT 3.5% CARBON, AND THE BALANCE SUBSTANTIALLY ALL IRON, THE IRON CONTENT NOT TO EXCEED 10%, FROM ABOUT 15% TO ABOUT 100% OF THE NICKEL CONSTITUENT OF THE ALLOY BEING PROVIDED AS CARBONYL NICKEL WHEN SAID ALLY IS PRODUCED, SAID ALLOY BEING CHARACTERIZED IN THAT THE CARBIDES EXISTING THEREIN ARE DISPERSED IN A METAL MATRIX WHEREBY WHEN SAID ALLOY IS EXPOSED TO ATTACK BY LEAD OXIDE AT HIGH TEMPERATURES, 